间伐和施肥对杉木人工林土壤温室气体排放的影响

Effects of thinning and fertilization on GHGs emissions in Chinese fir plantation soil

明确间伐强度和施肥对人工林土壤温室气体排放的影响,是准确评估人工林土壤温室气体排放能力的重要基础。以我国亚热带杉木(Cunninghamia lanceolata)人工林为对象,通过设置3种间伐强度(轻度、中度和重度)和2种施肥处理(不施肥和施肥)来研究间伐和施肥对杉木人工林土壤CO_(2)、CH_(4)和N_(2)O排放通量以及全球增温潜势的影响,并结合土壤理化性质阐明影响温室气体排放的主要因素。结果表明:与中度间伐相比,轻度间伐显著促进了土壤CO_(2)的排放和CH_(4)的吸收,施肥显著提高了轻度间伐土壤的Q_(10)值,施肥显著抑制了中度间伐土壤N_(2)O的排放,施肥与重度间伐共同处理显著促进了土壤CO_(2)与N_(2)O的排放以及CH_(4)的吸收;从全球增温潜势来看,重度间伐与施肥共同处理下的全球增温潜势最大,其次为轻度间伐处理,中度间伐处理最低。从整个观测期来看,杉木人工林土壤是大气CO_(2)和N_(2)O的源,是CH_(4)的汇;土壤湿度是影响CO_(2)排放和CH_(4)吸收的主导因素,其次为土壤N素有效性,而土壤N_(2)O的排放主要受土壤温度的调控;不同间伐强度和施肥处理通过改变土壤水热条件和N素有效性对杉木人工林土壤温室气体排放产生显著影响,中度间伐土壤具有良好的减排限排能力。

Understanding the effects of thinning intensity and fertilizer application on soil greenhouse gas emissions of forest plantations is important to accurate assessment of the capacity of greenhouse gas emissions from plantation soils.In this study,three levels of thinning intensity(mild,moderate,and severe)and two levels of fertilizer application(no fertilization and fertilization)were carried out in a subtropical Chinese fir(Cunninghamia lanceolata)plantation in China to investigate the effects of thinning intensity and fertilization on soil CO_(2),CH_(4)and N_(2)O emissions and global warming potentials(GWPs).Soil physicochemical properties were measured to clarify the main factors that regulating soil greenhouse gas emissions.The results showed that mild thinning intensity significantly increased soil CO_(2)emissions and CH_(4)absorption compared with moderate thinning intensity.Fertilization together with mild thinning intensity significantly increased soil temperature sensitivity(Q;).Fertilization combined with moderate thinning intensity significantly decreased soil N_(2)O emission,while fertilization combined with severe thinning intensity significantly increased soil CO_(2)and N_(2)O emissions and CH_(4)absorption.From the perspective of GWPs,the combined treatment of severe thinning intensity and fertilization had the largest GWPs,followed by mild and moderate thinning intensity.Throughout the observation period,Chinese fir plantation soil was CO_(2)and N_(2)O source,but CH_(4)sink.Soil moisture was the dominant factor regulating soil CO_(2)emission and CH_(4)absorption,followed by soil available N.Soil N_(2)O emissions were controlled by soil temperature.The results indicated that different thinning intensities and fertilization treatments had significant effects on soil greenhouse gas emissions and GWPs of Chinese fir plantations by changing soil moisture,temperature and N availability.Moderate thinning had better potential in reducing soil greenhouse gas emissions.